Collagen Biosynthesis in the Chick Embryo: I. The source of free proline and collagen hydroxyproline

This is the authors' abstract. We don't add key points for this paper.

The amounts of free proline, collagen-proline and collagen-hydroxyproline arising from glutamate, arginine and ornithine were determined in the legs of 10-day old chick embryos. Tissue minces were incubated in Ringer-Krebs buffer in the presence of radioactive precursor. Free amino acids and amino acids obtained after acid hydrolysis of collagen and of the non-collagenous residue were separated by ion exchange chromatography and quantified. Glutamate was not found to be a major precursor of free proline in the leg minces. Also, the radioactivity arising from labeled glutamate was low in collagen and in the aggregate non-collagenous proteins.On the other hand, arginine and ornithine were active precursors of free proline and free glutamate. Furthermore, the net amount of glutamate synthesized from either arginine or ornithine was much greater than the amount of proline synthesized from these amino acids. The proline and hydroxyproline in collagen were found to contain appreciable radioactivity arising from arginine and ornithine, suggesting that the free proline in the leg of the chick embryo is chiefly derived from these amino acids, and then becomes incorporated into collagen and other proteins. Hypotheses are considered conceining the contributions of arginine, ornithine and glutamate to the synthesis of free proline and proline in collagen.